Extrusion of Regular and Waxy Barley Flours for Production of Expanded Cereals

Grains of two regular and two waxy barley cultivars were milled into break and reduction stream flours using a wheat milling mill, granulated to facilitate feeding and flow through the barrel, and extruded to form expanded products using a modified laboratory single‐screw extruder. As moisture content of barley granules decreased from 21 to 17%, the expansion index of extrudates increased from 1.81 to 2.68, while apparent modulus of compression work (AMCW) decreased from 17.1 × 10⁴ to 7.8 × 10⁴ N/m². Break stream flours of both regular and waxy barley produced extrudates with higher expansion index (2.72–3.02), higher water absorption index (WAI), and lower AMCW than extrudates from reduction stream flours. Extrudates produced from regular barley had generally higher expansion and lower density than those produced from waxy barley. The specific mechanical energy (SME) was greater during extrusion of regular than of waxy barley. Barrel temperatures of 130, 150, and 170°C for the feeding, compression, and metering sections, respectively, resulted in higher SME, higher expansion index, lower water absorption index and lower AMCW of extrudates compared with a constant extruder barrel temperature of 160°C. Increased screw speed generally resulted in larger expansion index and increased WAI of extrudates. With increased feed rate from 89 to 96 g/min, the expansion index of extrudates decreased from 3.20 to 2.78 in regular barley and 3.23 to 2.72 in waxy barley, and harder extrudates were produced.     

Oil Absorption Characteristics of a Multigrain Extrudate During Frying: Effect of Extrusion Temperature and Screw Speed

The oil absorption characteristics of a multigrain extruded and fried snack product were studied as a function of extruder screw speed and cooking temperature using a central composite response surface methodology (RSM). The extruded product was produced using a corotating twin screw extruder, dehydrated to a uniform moisture content, and subsequently deep‐fat‐fried at 192 ± 1°C for 10–40 sec to complete expansion. Significant RSM models were developed for oil absorption and extrudate water absorption index (WAI). According to the lowest oil model, absorption (19.9%) was obtained with an extruder screw speed of 218.6 rpm and a cooking temperature of 117.8°C. WAI reached a maximum at a screw speed of 221.9 rpm and a cooking temperature of 109°C. Oil absorption characteristics and extrudate WAI were significantly correlated (r= ‐0.84, P = 0.0002). The data suggest that extrusion conditions can be optimized to influence the physicochemical structures in the extrudate matrix so that oil absorption can be minimized.     

Effect of Extruding Wheat Flour at Lower Temperatures on Physical Attributes of Extrudates and on Thiamin Loss When Using Carbon Dioxide Gas as a Puffing Agent

Wheat flour with 0.3% (w/w) thiamin was extruded on a twin‐screw laboratory‐scale extruder (19‐mm barrel) at lower temperatures and expanded using carbon dioxide (CO₂) gas at 150 psi. Extrusion conditions were die temperature of 80°C and screw speed range of 300–400 rpm. Control samples were extruded at a die temperature of 150°C and screw speed range of 200–300 rpm. Dough moisture content was 22% in control samples and 22 and 25% in CO₂ samples. Expansion ratio, bulk density, WAI, and %WSI were compared between control and treatment. CO₂ injection did not significantly increase expansion ratio. Bulk densities in the CO₂ extruded samples decreased when feed moisture decreased from 25 to 22%. The products using CO₂ had lower WAI values than products puffed without CO₂ at higher temperatures. The mean residence time was longer in CO₂ screw configurations than in conventional screw configurations. Thiamin losses were 10–16% in the control samples. With CO₂, thiamin losses were 3–11% at 22% feed moisture, compared with losses of 24–34% at 25% moisture. Unlike typical high‐temperature extrusion, thiamin loss in the low‐temperature samples decreased with increasing screw speed. Results indicate that thiamin loss at lower extrusion temperatures with CO₂ injection is highly dependent on moisture content.     

Selected Functional Properties of Extruded Starch Acetate and Natural Fibers Foams

Response surface methodology was employed to study the functional properties of starch acetate foams blended with 0, 7.5, and 15% wood, oat, and cellulose fibers. The blends were extruded with 14, 17, and 20% ethanol as a blowing agent, using a twin‐screw extruder with 160°C barrel temperature and 225 rpm screw speed. Physical characteristics of the extrudates including radial expansion ratio, unit density, and bulk density; and mechanical properties including unit spring index and bulk spring index were determined. Scanning electron micrographs were taken to observe foam cell textures. Higher fiber content resulted in lower radial expansion. Ethanol content had a positive effect on foam expansion. Higher expansion was obtained in starch acetate‐cellulose foams because better starch acetate‐fiber matrix was formed. Mechanical properties increased with higher fiber and ethanol contents. Micrographs showed that uniform cell structures were associated with better mechanical properties.     

Effects of Processing Parameters on Physical Properties of Corn Starch Extrudates Expanded Using Supercritical CO2 Injection

Corn starch was extruded with a corotating twin-screw extruder (24:1 L/D ratio, 31-mm screw diameter) and supercritical CO₂ was injected as a blowing agent. The effects of barrel temperature (80–90°C), screw speed (150–250 rpm), and water injection (30–54 g/min) on specific mechanical energy (SME) input for the process and the physical properties of extrudates, such as expansion ratio, water absorption (WA), water solubility (WS), breaking stress, and elastic modulus, were examined using a response surface methodology. Barrel temperature had the greatest effect on physical properties of extrudates but not on SME input, whereas screw speed and water injection had significant effects on SME input. Extrudates had a smooth surface, and air cells were uniform and closed, providing low WA and WS. Using superimposed contour plots, optimum barrel temperature, screw speed, and water injection rate, based on maximum expansion ratio and minimum SME input, were 94–96°C, 155–175 rpm, and 36–39 g/min, respectively.     

Chemical Composition,Pasting, and Thermal Properties of 22 Different Varieties of Peas and Lentils

Eleven green pea, five yellow pea, and six lentil varieties were analyzed for their composition and pasting and thermal properties. Lentils had higher protein content (25.8–28.6%) than peas (22.2–27.6%). However, peas had higher fiber content (19.8–31.4%) than lentils (17.8–21.8%). Both peas and lentils showed similar starch content (41.5–52.3 and 43.5–50.0%, respectively), and they were both low in fat (<1.6%). Micro‐Visco‐Amylograph tests showed C‐type amylograph patterns, except for Richlea variety. Thermal properties of flours were measured at 20, 40, 60, and 80% moisture content with a differential scanning calorimeter. Linear trends with a decrease in peak temperatures (T _p) were observed with an increase in moisture from 20 to 60%, and beyond 60% T _p was constant. Currently, peas and lentils are sold by mixing different varieties into classes based on the similarities in color and size of the seeds. However, significant differences were observed in chemical compositions and pasting and thermal properties among varieties tested. This suggests that it may be a good practice to use single varieties or group varieties based on their composition and functional properties, so that the end user may have a consistent final product when using the peas.     

Effect of Extrusion Conditions on Pasting Behavior and Microstructure of Refabricated Rice: A Response Surface Analysis

The effects of moisture, screw speed, and barrel temperature on pasting behavior of refabricated rice grains were investigated in a corotating twin‐screw extruder with response surface methodology. The rice flour obtained from broken rice (≤1/8 of actual kernel size) of PR‐116 variety was used in the study. The screw speed was set at five levels between 49 and 150 rpm, barrel temperature between 59 and 110°C, and feed moisture between 31 and 45%. All pasting properties of refabricated grains evaluated—peak viscosity, hold viscosity, breakdown viscosity, final viscosity, and setback viscosity—were significantly (P < 0.01) affected by the three process variables. Barrel temperature was the most significant variable, with quadratic effect on all viscosity parameters. Response surface regression models were established to correlate the viscosity profile of refabricated rice grains to the process variables. The optimum moisture content, screw speed, and barrel temperature estimated by a response surface of desirability function for the production of refabricated rice were 36%, 130 rpm, and 89.5°C, respectively. Scanning electron microscopy also revealed that intermediate moisture and temperature along with high screw speed during extrusion could create a more realistic appearance of refabricated rice with less rupture of starch granules.     

Effect of organic residue amendment on mineralization of nitrogen in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of nitrogen (N) in rice soils amended with organic residues under flooded condition. A lab incubation study with a 3x3 factorial design (two replications) was conducted with three rice soils (Joydebpur, Faridpur, and Thakurgaon) receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), or 3) pea vine (Pisum sativum L.). The organic residue (25 mg straw g^‐1 soil) was mixed with soil and glass beads (1:1, soil to beads ratio), and transferred into a Pyrex leaching tube, flooded and then incubated at 35°C for up to 12 weeks. The soils in the leaching tubes were leached (while maintaining flooded condition) at 1,2,4, 8, and 12 weeks with deionized water for determination of NH₄‐N, NO₃‐N, pH, and Eh. Nitrogen mineralization in soils amended with rice straw was somewhat different than that of soils treated with pea vine. Soil treated with rice straw had a higher N mineralization rate than soils treated with pea vine, which was due to a lower carbon (C):N ratio for rice straw. The potentially mineralizable N pool (N_o) in soils amended with rice straw and pea vine under flooded conditions, estimated using a 1st order exponential equation, were 7 to 15 times, and 3 to 9 times greater for rice straw N_o values and pea vine, respectively, than the control. The K_N values for unamended soils ranged from 0.35 to 0.52 mg N kg^‐1 wk^‐1 and rice straw and pea vine treated soils were from 0.75 to 1.22 and 0.46 to 0.58 mgN kg^‐1 wk^‐1. The lower N_o and K_N values in pea vine treatments suggested there was greater immobilization of N than in rice straw treatments.     

Role of Blowing Agents in Expansion of High‐Amylose Starch Acetate During Extrusion

High‐amylose starch acetate (DS 2) was processed in a Brabender twin‐screw extruder with ethanol and isopropanol as blowing agents at concentrations of 0, 2, 5, 10, 15, and 25%. A constant temperature of 150°C, a constant screw speed of 140 rpm, and a die nozzle with diameter of 4.0 mm and length of 16.2 mm were used to study the role of blowing agents on the expansion of the extrudates. Extrudates without blowing agent shrunk considerably after exiting the die as the cells collapsed drastically after expansion. Stable radial expansion of the extrudates increased with increase in the ethanol concentration to an optimum value of 18.0 at 5% (db) ethanol concentration and decreased with further increase in the ethanol concentration. Stable radial expansion increased to a maximum of 17.0 as the concentration of isopropanol was increased to 25% (db), though the rate of increase in expansion decreased with the increase in isopropanol concentration >10%. Flashing off of blowing agents aided in removing the heat generated during extrusion. The faster the extrudate cooled, the less likely it was to shrink. SEM were used to observe the effects of concentration of blowing agents on cell morphology. Various phenomena involved during the expansion are discussed. To obtain an extrudate with high expansion and low density, isopropanol at 15–25% (db) was found most suitable in this study.     

Effects of Extruder Screw Speeds on Physical Properties and In Vitro Starch Hydrolysis of Precooked Pinto,Navy, Red,and Black Bean Extrudates

Precooked pinto, navy, red, and black bean flours were extruded at different screw speeds (320, 380, and 440 rpm) with a twin‐screw extruder. Effect of speed on physical properties and in vitro starch hydrolysis was investigated. Increasing screw speeds reduced water activity, expansion index, and texture. Extrudates could not be obtained from pinto bean flour at 440 rpm because of the high shear effect. Water absorption index and water solubility index were not significantly affected by screw speed but were significantly higher than for unextruded precooked flour. A significant change in color was observed in navy beans, characterized by increasing b values on the Hunter color scale. Resistant starch ranged from 3.65 to 4.83% db and was not significantly affected by screw speed. Glycemic index of all extrudates was high, ranging from 81.3 to 86.9.     

Extrusion Processing of Rice‐Based Breakfast Cereals Enhanced with Tocopherol from a Chinese Medical Plant

Brown rice flour was mixed with a Chinese medical plant (Euryale ferox Salisb.) and processed to make ready‐to‐eat breakfast cereals using twin‐screw extrusion. Levels of 15 and 20% feed moisture in flour, and 200 and 250 rpm screw speed were set, and the physicochemical properties and content of α‐, β‐, γ‐, and δ‐tocopherols were determined. The data showed that 15% feed moisture gave a low bulk density and water absorption index but a high expansion ratio and water solubility index. High screw speed (250 rpm) produced a result similar to that of 15% feed moisture. A sample with 85% brown rice flour with 15% E. ferox Salisb. retained the highest content of α‐, β‐, γ‐, and δ‐tocopherols (125, 6, 78, and 9 μg/g), respectively. The optimum extrusion conditions determined were 15% E. ferox Salisb. mixed with brown rice at 15% feed moisture and at 250 rpm screw speed.     

Influence of soil humic substances and herbicides on the growth of pea (Pisum sativum L.) in nutrient solution 1

No morphological and length modifications of the root and shoot systems are apparent in pea (Pisum sativum L.) plants of three varieties grown in the presence of 100 mg/L humic acid or fulvic acid or 20 mg/L linuron [3‐(3,4‐dichlorophenyl)‐l‐methoxy‐l‐methylurea] or ametryne [2‐ethylamino‐4‐iso‐propylamino‐6‐methylthio‐1,3,5‐triazine]. A combination of humic substance and herbicide at these concentrations produces in all pea varieties a differentiated and marked reduction in root length and large morphological alterations of roots. Statistical analysis of data show that differentiated and highly significant or significant effects are produced on the shoot and root dry weight by either the humic substance or herbicide alone, and by any combination of two or three factors considered (variety, humic substance, herbicide).     

河西绿洲灌区间作绿肥及其不同利用方式对玉米产量及土壤肥力的提升效应

[目的]研究玉米间作不同绿肥及绿肥不同利用方式在河西绿洲灌区的生产效益.[方法]田间定位试验始于2009年,该试验为河西绿洲灌区的典型种植模式,至取样时试验已进行12年.与玉米间作的绿肥作物包括针叶豌豆、甜豌豆、草木樨,每种绿肥均采用压青与根茬还田两种方式,以玉米单作为对照(CK).测定了玉米和绿肥生物量、产量构成因素...     

Effect of Particle Size and Moisture Content on Viscosity of Fish Feed

A model was developed for the influence of particle size on the extrusion of a fish feed and the physical characteristics of the extrudates evaluated. The study was conducted using factorial experiments in a fractional replication design for four variables with three levels, and one‐third of the replicates (3⁴ factorial in 27 units) were examined in a laboratory extruder. The torque‐screw speed measurement was used to develop a viscosity model equation that considered different shear rates, product temperature, initial moisture content, and particle size. When particle size decreased, the apparent viscosity became smaller. The barrel pressure was important in producing extrudate with a uniform volume over the range of processing conditions tested because it had a strong correlation with the volumetric expansion. The material with lower moisture and larger particles caused the specific mechanical energy to increase. The viscosity model developed in this study can be applied to the development of large‐scale extrusion models that determine the effect of particle size on the feed material extrudates.     

Effect of Hybrid and Physical Properties of Individual Popcorn Kernels on Expansion Volume

The relationships between expansion volume and physical properties of three varieties of popcorn kernels were investigated on a single kernel basis. Physical properties studied were kernel size, kernel sphericity, and kernel density. Methods of measuring densities and popped volumes of individual popcorn kernels were developed. Popcorn kernels were separated into seven kernel sizes by screening with round‐hole sieves. Thirty kernels from each of three kernel sizes (4.76 < D < 5.16, 5.56 < D < 5.95, 6.35 < D < 6.75 mm) of three popcorn varieties were individually measured for sphericity, density, and popped volume. Density and sphericity measures of popcorn kernels showed little variability. Variety, kernel sphericity, and kernel density had minor effects on expansion volume. Kernel size had no effect. There were no strong linear relationships (R² = 0.28) among expansion volume and physical properties of the three varieties of popcorn kernels. The variety with the highest mean density and the highest mean sphericity showed a tendency of producing higher mean expansion volumes.     

Twin-Screw Extrusion Processing of Feed Blends Containing Distillers Dried Grains with Solubles (DDGS)

Extrusion trials were conducted with varying levels of distillers dried grains with solubles (DDGS) along with soy flour, corn flour, fish meal, vitamin mix, mineral mix, and net protein content adjusted to 28% using a Wenger TX-52 twin-screw extruder. The properties of extrudates were studied in experiments conducted using a full-factorial design with three levels of DDGS content, two levels of moisture content, and two levels of screw speed. Increasing the DDGS content from 20 to 60% resulted in a 36.7% decrease in the radial expansion, leading to a 159 and 61.4% increase in the unit density and bulk density of the extrudates, respectively. Increasing the DDGS content resulted in a significant increase in the water absorption index (WAI) but a significant decrease in the water solubility index (WSI) of the extrudates. Changing the screw speed and moisture content had no significant effect on the radial expansion ratio but resulted in a significant difference in the bulk density of the extrudates, which may be due to the occurrence of longitudinal expansion. Even though changing the moisture content and screw speed had no significant effect on the WSI of the extrudates, significant differences in the WAI of the extrudates were observed. The ingredient components in the blend and moisture content had an influence on the color changes of the extrudates, as did the biochemical changes occurring inside the barrel during processing. Overall, it was determined that DDGS could be included at a rate of up to 60% using twin-screw extrusion, and that viable pelleted floating feeds can be produced.     

Effect of Free Fatty Acids Addition on Corn Grits Extrusion Cooking

The influence of added fatty acids on extrusion cooking of corn grits and extrudate properties was studied. Samples with three average corn grits particle sizes were processed in a twin-screw extruder; fatty acids content (0.2–0.8%, wb) varied, and experimental conditions were kept constant (moisture content 18.4% wb, barrel temperature 150°C, screw speed 165 rpm). The effect of adding fatty acids was studied by analyzing water solubility and absorption indices, expansion indices, and mechanical (puncture test) and structural (computerized image analysis) extrudate properties. When fatty acids were added, water solubility and absorption indices decreased, radial expansion index decreased, longitudinal expansion index increased, number of cells increased, and mechanical resistance of extrudates decreased. The influence of added fatty acids was attributed to the formation of fatty acids-amylose complexes.     

Estimated yield and nutrient contributions of legume cover crops intercropped with yam,cassava, and maize in the Benue River basins of Nigeria

Intercropping trials were established in the sandy soils of the Benue River Basins of Nigeria to assess the effect of some food legumes used as cover crops in cassava, yam, and maize based cropping systems. The soil productivity and yield contributions of ground akidi (Sphenostylis stenocarpa), pigeon pea (Cajanus cajan), local (Kafanji), and improved (IAR‐355) cowpea (Vigna unguiculata) varieties to the main crops were assessed and presented on a fertilizer‐ equivalent basis. The cowpea varieties and ground akidi helped maize to increase the efficiency of nitrogen (N)‐phosphorus (P)‐potassium (K) fertilizer use by producing an additional 2.74 and 1.59 kg grains/kg, respectively. While an additional six tons of yam tubers was contributed by the kafanji intercrop per hectare, only about three tons was contributed by ground akidi. With the exception of pigeon pea, the test legumes were suitable for use as cover crops for cassava, yam, and maize in the Benue River Basins of Nigeria.     

Effect of Barley Flour on Development of Rice‐Based Extruded Snacks

This study was conducted to develop a ready‐to‐eat extruded food using a single‐screw laboratory extruder. Blends of Indian barley and rice were used as the ingredients for extrusion. The effect of extrusion variables and barley‐to‐rice ratio on properties like expansion ratio, bulk density, water absorption index, hardness, β‐glucan, L*, a*, b* values, and pasting characteristics of extruded products were studied. A central composite rotatable design was used to evaluate the effects of operating variables: die temperature (150–200°C), initial feed moisture content (20–40%), screw speed (90–110 rpm), and barley flour (10–30%) on properties like expansion ratio, bulk density, water absorption index (WAI), hardness, β‐glucan, L*, a*, b* values, and sensory and pasting characteristics of extruded products. Die temperature >175°C and feed moisture <30% resulted in a steep increase in expansion ratio and a decrease in bulk density. Barley flour content of 10% and feed moisture content of <20% resulted in an increased hardness value. When barley flour content was 30–40% and feed moisture content was <20%, a steep increase in the WAI was noticed. Viscosity values of extruded products were far less than those of corresponding unprocessed counterparts as evaluated. Rapid visco analysis indicated that the extruded blend starches were partially pregelatinized as a result of the extrusion process. Sensory scores indicated that barley flour content at 20%, feed moisture content at 30%, and die temperature at 175°C resulted in an acceptable product. The prepared product was roasted in oil using a particular spice mix and its sensory and nutritional properties were studied.     

Rangeland Use Change to Agriculture Has Different Effects on Soil Organic Matter Fractions Depending on the Type of Cultivation

The agricultural use of natural ecosystem is increasing in the Middle East because of population growth in the most countries. The type of cultivation could affect the content of soil organic matter in the rangeland use changes into agriculture. Therefore, we compared soil organic matter fractions of semi‐arid rangelands with agricultural lands (wheat‐land, pea‐land and orchard) where have been changed from semi‐arid rangelands to agriculture 15 years before. The results showed that in general, total and particulate organic matter (TOM and POM) and total nitrogen (TN) were highest in the rangeland compared with the three‐agricultural lands in intact soil, macro‐aggregates and micro‐aggregates (p < 0·05). Nevertheless, TOM content in orchard (1·45%) was higher than the two other land uses, and there was no significant difference of TN between natural rangeland and orchard in intact soil. The highest values of POM were obtained in the rangeland (0·23%) and orchard (0·22%), and the lowest value of POM was obtained in the pea‐land (0·14%) and wheat‐land (0·08%) in macro‐aggregates. In micro‐aggregates, TOM, POM and TN were highest in the rangeland (1·77%, 0·23% and 0·19%, respectively) and showed similar pattern in the three‐agricultural lands. We discussed that compared with pea‐land and wheat‐land, orchard was received less negative impact on soil qualitative parameters in land use changes projects from rangeland into agriculture. We conclude that orchard could be a better option in rangeland use changes into agriculture compared with the other cultivations. Copyright © 2016 John Wiley & Sons, Ltd.